The present invention relates generally to ultraviolet (UV) cured coatings, and more particularly to UV curable coating compositions, processes of their use, and as well to coated articles resulting therefrom.
Conventionally cured hardcoat finishes have several disadvantages. In general, the coating materials and the curing agent must be applied separately, in a particular sequence and at particular relative levels. Because both the proportions of the ingredients and the timing of their application is critical, conventionally cured hardcoats have been difficult and costly to apply, especially with the consistency and uniformity required in current commercial applications.
UV cured coatings overcome several disadvantages associated with conventional hardcoat finishes. In particular, UV curable coating compositions may be premixed, e.g. the polymerization initiator is added to the active ingredients by the manufacturer when the coating is produced, and not by the coating user when the coating is about to be applied. Thus, mixing and measurement errors can be avoided and a more consistent product can be obtained.
Despite their many advantages, UV curable coating compositions themselves pose problems which must be addressed. For example, typical UV hardcoats are high molecular weight, highly crosslinked films which are formed from the highly reactive acrylate functionality. As such, known UV hardcoats have suffered from limited durability, low solids content and cured resin shrinkage. They have also required high doses of UV light to cure. Other UV hardcoats formulated in an attempt to overcome these problems typically suffer from some combination of loss of abrasion and scratch resistance, poor processibility and unsatisfactory durability. A need therefore exists for a UV curable product which is conveniently processable and which forms cured coatings exhibiting improved physical and chemical properties, e.g. scratch and abrasion resistance, and durability.